December in Walla Walla is the coldest month of the year. In December, the weather in Walla Walla is typically cold. Average daily high temperature in December is about 3 degrees above zero. On average, Walla Walla has 9 rainy, 9 partly cloudy, 7 cloudy, and 6 sunny days in December. The rains are usually moderate. December as well as January, February, March, and November is considered the most uncomfortable time to visit Walla Walla.